This chapter presents different proofs of the existence of external objects, but proofs which are in important respects of a different sort from those just given. It emphasizes that, when I. Kant says it is a scandal not to be able to give a proof of the existence of external objects, a proof of their existence in the past would certainly help to remove the scandal of which he is speaking. Some people understand 'proof of an external world' as including a proof of things which the author hasn't attempted to prove and hasn't proved. The chapter makes the meaning of 'external things' clearer still if the author explains that this phrase has been regularly used by philosophers as short for 'things external to our minds'. There has been a long philosophical tradition, in accordance with which the three expressions 'external things', 'things external to us' and 'things external to our minds' have been used as equivalent to one another.